Various types of exercises have been created for exercising particular muscles of the human body. For example, one relatively popular exercise for exercising the muscles of the abdomen and core is known as a plank. During such an exercise, a person places his or her body in a prone position or pushup position with legs straight or bent and having toes or knees touching a support surface while supporting the upper body with the hands (pushup position) or the forearms (plank position) on a support surface. The idea is to hold the body in an erect horizontal position using the core muscles to stabilize the body.
Variations of this exercise include using one arm or hand to support the body in a sideways position (known as the “side plank”) and the reverse plank where the body is flipped upside down with the arms facing the back of the user and the heels of the body contacting the support surface while the user is facing upwards.
The plank exercise is sometimes performed on a support surface such as a floor and sometimes on a towel or exercise mat to prevent sliding. The plank exercise in the past has been performed on a wobble board type device. When performing a plank on a wobble board on a floor, however, if the user tilts from side to side, the wobble board tends to slide across the floor, forcing the user to have to move his or her feet to stay properly aligned with the wobble board.